import { JSONWebToken, Ticket, User, Credential, CredentialId, Base64UrlString, Base64Url } from '@digitalpersona/core';
import { IAuthService, AuthenticationStatus } from '@digitalpersona/services';
import { HandshakeStep, HandshakeContext } from './handshake';

export class AuthenticationData
{
    public readonly handle: number;
    public readonly data: string;
}

export interface IAuthenticationClient
{
    init(): Promise<AuthenticationData>;
    continue(handle: number, data: string): Promise<Base64UrlString>;
    term(handle: number): Promise<void>;
}

/** @internal */
export abstract class Authenticator
{
    constructor(
        protected readonly authService: IAuthService,
        protected readonly authClient?: IAuthenticationClient,
    ) {
        if (!this.authService)
            throw new Error("authService");
    }

    protected _authenticate(
        identity: User|JSONWebToken|null,
        credential: Credential|CredentialId,
    )
    : Promise<JSONWebToken>
    {
        return authenticate(identity, credential, this.authService, this.authClient);
    }
    public _identify(cred: Credential): Promise<JSONWebToken> {
        return this.authService
            .Identify(cred)
            .then(ticket => ticket.jwt);
    }
}

/** @internal */
function authenticate(
    identity: User | JSONWebToken | null,
    credential: Credential | CredentialId,
    server: IAuthService,
    client?: IAuthenticationClient,
): Promise<JSONWebToken>
{
    // When credential data are present, use a direct authentication flow
    if (credential instanceof Credential) {
        if (!identity) identity = User.Everyone();
        return (identity instanceof User
            ? server.Authenticate(identity, credential)
            : server.Authenticate(new Ticket(identity), credential)
        ).then(ticket => ticket.jwt);
    }

    // When no credential data are present, use a challenge-response authentication flow
    if (!client)
        return Promise.reject(new Error("Client"));

    // Performs one step in an authentication workflow and recursively calls itself for a next step.
    // The workflow finishes when a token obtained, or an error produced.
    const nextStep = (ctx: HandshakeContext): Promise<JSONWebToken> =>
    {
        switch (ctx.nextStep())
        {
            case HandshakeStep.InitClient: { return client
                .init()
                .then(data => nextStep(ctx.withClientHandle(data.handle).withClientData(data.data)));
            }
            case HandshakeStep.InitServer: {
                return ((identity === null) || (identity instanceof User)
                    ? server.CreateAuthentication(identity, credential)
                    : server.CreateAuthentication(new Ticket(identity), credential))
                .then(handle => nextStep(ctx.withServerHandle(handle)));
            }
            case HandshakeStep.ContinueClient: { return client
                .continue(ctx.clientHandle, ctx.serverData!)
                .then(clientData => nextStep(ctx.withClientData(clientData)));
            }
            case HandshakeStep.ContinueServer: { return server
                .ContinueAuthentication(ctx.serverHandle, Base64Url.fromUtf8(ctx.clientData!))
                .then(result => {
                    switch (result.status) {
                        case AuthenticationStatus.Error:
                            return Promise.reject(new Error("Authentication failed"));
                        case AuthenticationStatus.Continue:
                            return nextStep(ctx.withServerData(result.authData));
                        case AuthenticationStatus.Completed:
                            return Promise.resolve(result.jwt);
                        default:
                            throw new Error("Unexpected status");
                    }
                });
            }
        }
    };

    // Start the workflow and extract a token (or throw an error) when ready.
    const context = new HandshakeContext();
    return nextStep(context)
        .catch(err => {
            // somehow exception thrown inside u2fApi does not automatically reject the promise, so forcing this here
            return Promise.reject(err);
        })
        .finally(() => {
            if (context.clientHandle) client.term(context.clientHandle);                     // ignore the outcome
            if (context.serverHandle) server.DestroyAuthentication(context.serverHandle);    // ignore the outcome
        });
}